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題名 | Saltating Characteristics of Particle Motions Near the Channel Bed=近床區域顆粒躍移運動之研究 |
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作 者 | 李鴻源; 許盈松; | 書刊名 | Proceedings of the National Science Council : Part A, Physical Science and Engineering |
卷期 | 22:4 1998.07[民87.07] |
頁次 | 頁480-491 |
分類號 | 443 |
關鍵詞 | 近床區域; 顆粒躍移運動; Sediment transport; Bed load transport; Saltation; Real-time flow visualization technique; High-speed photographic technique; |
語文 | 英文(English) |
中文摘要 | 水流中近床區域泥砂顆粒躍移機制的研究對於推移載運動理論的發展具有重要的 意義。本研究運用「即時-流場顯影技術」與「高速攝影技術」,能在不影響流況的情況下, 同時量測許多傳統方法所無法測得之數據,包括泥砂運動軌跡、運動速度及旋轉速度。試驗 過程中採用不同顆粒條件和不同水流強度的組合,系統地量測了底床附近顆粒的躍移過程, 得出在不同水流強度下躍移顆粒之最大躍高、最大躍長、縱向躍移平均速度及躍移旋轉速度。 本文同時提出顆粒單步躍移歷程之物理摸式,在已知水流及顆粒條件下,本模式可模擬 顆粒躍移軌跡與躍移過程中之速度、加速度及各作用力之沿程變化特性。與試驗結果相驗證, 發現本文所建立的物理模式對近床區域泥砂顆粒躍移特性之模擬相當準確,同時發現躍移過 程中的馬格納斯效應為一不可忽略的因素,應該加以考慮。經由本文之研究,可以清楚瞭解 躍移顆粒之運動特性,對往後進一步深入探討底床質輸砂量推估之理論研究,有極大的助益。 |
英文摘要 | A real-time flow visualization technique and a high-speed photographic technique were developed in this study to measure particle trajectories, velocities, and spinning rates. Different combinations of water depths, channel slopes, particle sizes, particle shapes, and particle densities were tested. Regression equations for the dimensionless average saltation length. Height, and velocity, lift-off spinning rates and longitudinal variations of the spinning rates were obtained. A mathematical model which is able to simulate particle single-step saltation behaviors is developed herein. This model is able to calculate the particle trajectories and the longitudinal variations of the velocities, accelerations, and corresponding forces acting upon the particle. The simulated saltation trajectories agree well with the experimental data. It is also found that the Saffman force and Magnus force play a very important role in the saltation process and, hence, cannot be neglected. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。